Interruption of railway traffic creates important financial losses for the transportation utilities and society at large. At this moment, to limit this impact, the CN uses emergency girders stored around their territory to decrease the time to transport the materials to the site. However, this method is difficult to put in place and bypass of the traffic is not possible everywhere. The development of a portable railway bridge is interesting for this purpose. This structure has to be transported, erected and in services within 48h. This type of bridge should also be adjustable in length to allow reusing of the existing bearings, piers and abutments (5 to 28m of span). Between the steel superstructure possibilities, three solutions have been chosen: (a) plate girder, (b) through girder and (c) through truss. The geometry and the construction method are the particularities to consider. After those conceptions, the three alternatives have been analyzed as a function of many criteria. The number of bolts, the quantity of material and the dimension of the prefabricated sections were considered to determine the best solution for this kind of utilization.

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The world-wide development of new high-speed rail lines has led to more stringent design requirements for railway bridges, mainly because high-speed trains can cause resonance in the bridge superstructure. Dynamic simulations, often utilising time-consuming finite element analysis (FEA), have become essential for avoiding such problems. Therefore, guidelines and tools to assist structural engineers in the design process are needed. Considerable effort was spent at the beginning of the project, to develop simplified models based on two-dimensional (2D) Bernoulli-Euler beam theory. First, a closed-form solution for proportionally damped multi-span beam, subjected to moving loads was derived (Paper I). The model was later used to develop design charts (Paper II) and study bridges on existing railway lines (Paper III). The model was then extended to non-proportionally damped beams (Paper IV) in order to include the effects of soil-structure interactions. Finally, the importance of the interaction between the surrounding soil and the bridge was verified by calibrating a finite element (FE) model by means of forced vibration tests of an end-frame bridge (Paper V). Recommendations on how to use the models in practical applications are discussed throughout the work. These recommendations include the effects of shear deformation, shear lag, train-bridge and soil-structure interactions, for which illustrative examples are provided. The recommendations are based on the assumption that the modes are well separated, so that the response at resonance is governed by a single mode. The results of the work show that short span bridges, often referred to as `simple´ bridges, are the most problematic with respect to dynamic effects. These systems are typically, non-proportionally damped systems that require detailed analyses to capture the `true´ behaviour. Studying this class of dynamic system showed that they tend to contain non-classical modes that are important for the structure response. For example, the bending mode is found to attain maximum damping when its undamped natural frequency is similar to that of a non-classical mode. / <p>QC 20170213</p>

The bump at the end of the railway bridge is a result of differential movement between the bridge deck and the approach embankment. The movement can have the form of a bump or a dip. Either defect in the track geometry can cause significant problems in track performance. The current state of practice was evaluated by conducting a literature review and an industry survey. According to the survey, approximately half of all railway bridges are affected by the bump/dip. The total annual cost for repairing these bridge transition problems is estimated at $26 million. This does not take into account the considerable cost resulting from speed reductions that railroads must place on trains at these locations. In addition to the increased maintenance costs, the bump/dip leads to higher impact loads, uncomfortable rides and possible safety hazards. The track response due to the bump at the end of the bridge was evaluated by creating a 4-D finite element model of the train, track structure and track substructure. The motion of the train model across a bridge/approach transition, with and without a bump/dip, was then simulated using LS-DYNA. It was found that a track modulus differential alone (no bump/dip) at a bridge/approach location leads to impact forces as well as increased ballast and subgrade pressures on the approach. This instigates the formation of a bump or dip in the track. The track response is increased when a bump/dip is present in the track profile. A parametric study looking at the influence of train direction, train speed, bump/dip size, approach embankment soil modulus, approach tie material, bridge tie material, bridge deck type, ballast thickness and approach tie length on the magnitude of impact forces, track deflection, ballast and subgrade pressures was also performed with the model. Finally, a design solution to minimize the bump at the end of the bridge is proposed. The solution involves installing varying length steel bars into a soft subgrade approach embankment. The solution addresses both the settlement and track modulus differential between the bridge and the embankment. A full-scale field test of this prototype solution is underway.

In the current thesis, the Banafjäl Bridge located on the Bothnia line (Botniabanan) in northern Sweden was studied. The bridge is a 40m long composite ballasted high-speed railway bridge. A 3D FE model of the bridge was developed using a commercial FE software, Abaqus. The FE model was calibrated against the measured data of the bridge. The dynamic response of the bridge's FE model was investigated under the dynamic load of the passing HSLM-A train using modal dynamic analysis. The vertical acceleration induced by excitation of the passing train exceeded the permissible limit of 3.5 m/s2 for the speed range of 220-240 km/h. Thus, damping solutions using multiple tuned mass dampers (MTMDs) were investigated. According to the results of this study, a 4 tonnes MTMD system consist of 5 parallel TMDs attached to the mid-span of the bridge could effectively control the undesired vibration of the bridge. The suggested solution could account for the changes in the stiffness of the bridge caused by freezing and ice forming in the ballast.

The economic and technologic development experienced by the society in the last decades has caused the demand of a new type of faster and more comfortable transport. This type of demand has been covered by the air transport, the road transport and the railway transport. This situation where the society demands an improvement in her quality of life is the best situation for the birth of the high speed trains. Different studies carried out in the transport field have demonstrated that for distances between four hundred and one thousand of kilometres, the high speed trains provide a lower travelling times than the rest of the transports. These types of high speed trains have increased the axle loads and the average speeds, thus generally a dynamic analysis is required by the ERRI in all the railway bridges when the train speed is higher than 200 Km/h. Besides, when the train speed is going to be higher than 200 Km/h, the vibrations induced in the bridge can reduce the service life of the vehicles and structure, and generally, this fact leads to become the dynamic effect in the principal factor to take into account in order to design the structure. Therefore, an important knowledge in railway bridges dynamic is required to not to oversize the structures with the consequent economic cost. The purpose of this thesis is to study the possibility of accurately predicting the dynamic response of an existing railway bridge, subjected to the high speed train Gröna Tåget, implementing a simplified 2D finite element model with the aid of the program Abaqus. The bridge chosen is the Lögdeälv Bridge, a two spans composite bridge, located along the Bothnia Line (the new Swedish high-speed line), between the localities of Nordmaling and Rundvik. The measured eigenfrequencies due to bending modes of vibration are used for updating the model and then, these frequencies and the accelerations measured are used to compare and validate the different 2D updated models. The parameters used to update the models are; the damping coefficient of the structure, the mass and the stiffness of the bridge, and the supports stiffness. Finally it is concluded that the best model is achieved when the rotational support stiffness is modified in the two extremes supporters of the bridge.

Research performed on the subject of dynamic soil-structure interaction (SS) concerning railway bridges is presented in this thesis with the focus on simply supported railway bridges supported by shallow foundations in soil strata on bedrock. The research aims to obtain insight into the SSI of high-speed railway bridges and to provide recommendations on how to model the soil-bridge system from a design perspective. A three-dimensional (3D) simply supported soil-bridge model was first developed and the effects from model assumptions made on the soil-foundation system was evaluated in a 3D setting (paper I). The soil-foundation system was then refined and a model assumptions study was performed in order to evaluate the effects of model assumptions on impedance functions, including the influence of the permanent load acting on the soil-foundation system (paper II). Finally, a study of the assembled soil-bridge system was performed in an extensive parametric study including a set of 2D bridge models in combination with a set of shallow foundations in soil strata on bedrock (paper III). A supplementary section related to paper III was also added in this thesis, showing the effects of the substructure mass. The model assumptions made when creating the soil-foundation model and the soil-bridge model can be very important and must be made with care. The permanent load acting on the soil-foundation systems of shallow foundations may alter the impedance functions significantly. The substructure mass may alter the behavior of the soil-bridge system depending on its magnitude, and neglecting it gives inaccurate results. The 3D effects of SSI do not cause high vibrations due to modes other than the first bending mode, and assuming a 2D bridge model is generally acceptable. The effects of SSI on the soil-bridge systems with shallow soil strata are largely dependent on the ratio between the natural frequency of the bridge and the fundamental frequency of the soil. Depending on the value of this ratio, the effect of including SSI in bridge models may contribute to the bridge obtaining a negligible, conservative, or non-conservative response, as compared to the bridge with the assumption of non-flexible supports. / Forskning i syfte att utröna effekten av dynamisk jord–struktur-interaktion (SSI)på järnvägsbroar presenteras i denna avhandling med huvudfokus på fritt upplagdabroar med stöd av plattgrundlagda fundament i jordar på fast berggrund. Forsknin-gen syftar till att ge förståelse för interaktionen mellan jord och järnvägsbroar samtatt ge rekommendationer på hur systemet kan modelleras ur ett designperspektiv.En tredimensionell (3D) fritt upplagd jord–bromodell utvecklades först och effek-terna av modellantaganden gjorda på jord–grundläggningssystemet utvärderadesi en 3D miljö (artikel I). Jord–grundläggningssystemet förfinades och en studiegenomfördes för att utvärdera effekterna av modellantaganden på impedansfunk-tioner, inklusive påverkan av den permanenta belastningen som verkar på jord–grundläggningssystemet (artikel II). Slutligen utfördes en omfattande parametriskstudie av det sammansatta jord–brosystemet där en uppsättning tvådimensionella(2D) bromodeller kombinerades med en uppsättning jordar (artikel III). Ett kom-pletterande avsnitt relaterat till artikel III lades till i denna avhandling som visareffekterna av massan av underbyggnaden på jord–brosystemet.De modellantaganden som görs vid skapandet av jord–grundläggningsmodeller ochjord–bromodeller kan vara mycket viktiga och bör utföras med varsamhet. Den per-manenta belastningen som verkar på jord–grundläggningssystemet kan väsentligtförändra impedansfunktionerna. Massan av underbyggnaden kan vidare ändra re-sponsen i jord–brosystemet, beroende på dess storlek, och att försumma den kan gefelaktiga resultat. De 3D effekterna av SSI orsakar inte höga vibrationer på grundav andra moder än den första böjmoden, och att anta en 2D bromodell är såledesgenerellt sett motiverat.Effekterna av SSI på jord–brosystemet i grunda jordar beror till stor del av kvotenmellan brons naturliga frekvens och jordens fundamentala frekvens. Beroende påvärdet på denna kvot kan effekten av att inkludera SSI i bromodeller bidra till attbron får en försumbar, konservativ, eller icke-konservativ respons, i jämförelse medbron med antagandet om fasta upplag. / <p>QC 20200903</p>

Since last few decades, the increased pressure from the environmental issues of natural resource depletion, global warming and air pollution have posed a great challenge worldwide. Among all the industrial fields, bridge infrastructures and their belonged construction sector contribute to a wide range of energy and raw materials consumptions, which is responsible for the most significant pollutions. However, current bridges are mainly designed by the criterion of economic, technique, and safety standards, while their correlated environmental burdens have unfortunately rarely been considered. The life cycle assessment (LCA) method has been verified as a systematic tool, which enables the fully assessment and complete comparison for the environmental impact among different bridge options through a life cycle manner. The study presented in this thesis is focused on railway bridges, as the LCA implementation is under great expectations to set a new design criterion, to optimize the structural design towards the environmental sustainability, and to assist the decision-making among design proposals. This thesis consists of two parts: an extended summary and three appended papers. Part one gives an overview introduction that serves as a supplementary description for this research work. It outlines the background theory, current development status, the LCA implementation into the railway bridges, as well as the developed excel-based LCA tool. Part two, includes three appended papers which provides a more detailed theoretical review of the current literatures and knowledge associated with bridge LCA, by highlighting the great challenging issues. A systematic flowchart is presented both in Paper I and Paper II for how to model and assess the bridge life cycle, together by coping with the structural components and associated emissions. This flowchart is further illustrated on a case study of the Banafjäl Bridge in Sweden, which has been extensively analyzed by two LCA methods: CML 2001 method and streamlined quantitative approach. The obtained results can be contributed as an analytical reference for other similar bridges. Based on the theoretical review and analytical results from case studies, it has been found that the environmental profile of a bridge is dominated by the selected structural type, which affects the life cycle scenarios holistically and thus further influences the environmental performance. However, the environmental profile of the structure is though very case specific; one cannot draw a general conclusion for a certain type of bridge without performing the LCA study. The case study has found that the impact of material manufacture phase is mostly identified significant among the whole life cycle. The availability of the inventory data and project information are appeared as the major problem in the bridge LCA study. Moreover, lack of standardized guideline, criteria and input information is another key issue. A criterion is needed to illustrate what are the qualified limits of a bridge to fulfill the environmental requirements. Therefore, the development of LCA for railway bridges still needs further collaborative efforts from government, industry and research institutes. / QC 20120227

The world-wide development of new high-speed rail lines has led to more stringent design requirements for railway bridges. This is mainly due to the fact that a train at high speeds can cause resonance in the bridge superstructure.  In order to avoid problems of this kind, it has become essential to perform dynamic simulations, which are usually carried out in a time consuming finite element program. The main reason for not using an analytical solution is that this type of solution only exists for simple bridges, e.g., simply supported bridges. The aim of this thesis, is therefore the development of a simplified analytical model for preliminary dynamic analyses of railway bridges. The model is then used in several studies, both parametric and probabilistic ones, to determine the dynamic response of various railway bridges under moving loads. Special attention is paid to acceleration levels in the bridge superstructure, because previous studies have shown that these are often decisive. In the design, both the model and the numerical simulations can be used with considerable effectiveness to help engineers to define their structural systems. All bridges, throughout this thesis, have been modelled with elastically supported multi-span Bernoulli-Euler beams. The amount of dissipated energy is modelled using modal damping. The train load is modelled by concentrated loads, which implies that the vehicle-bridge interaction is not considered. A model with these characteristics can be used to analyse simply supported concrete bridges as well as multi-span steel bridges. Another advantage of the proposed method is that the solution is exact, because the equation of motion has been solved using a Laplace transform. A lot of effort has been made to have a model both as simple as possible and flexible enough to be able to study a wide variety of structures. The results of the case studies have shown that concrete bridges are more suitable than steel and composite bridges for use in the new high-speed lines. The simulations have also shown that short-span railway bridges have problems in meeting the design requirements. This confirms the high acceleration levels that were recorded in France, just after the inauguration of the new high-speed line between Lyon and Paris, on several short-span bridges. Furthermore, it was found that a multi-span bridge has a reduction in its dynamic response of up to 60 % compared to a similar simply supported bridge. / Utbyggnaden av nya höghastighetsbanor i världen har resulterat i striktare krav vid dimensionering av järnvägsbroar. Orsaken är främst att tåg vid höga hastigheter kan orsaka resonans i brons överbyggnad. För att kontrollera dessa effekter krävs omfattande dynamiska simuleringar, vilket ofta utförs med tidskrävande FE-analyser. Med analytiska metoder kan beräkningstiden minskas dramatiskt, dessa är dock ofta begränsade till enkla elementarfall, t.ex. fritt upplagda balkar. Syftet med föreliggande avhandling är att utveckla flexibla hjälpmedel för dynamiska kontroller av järnvägsbroar. Avhandlingen fokuserar på accelerationer i brons överbyggnad eftersom tidigare studier har visat att det är den som ofta är dimensionerande. Utöver detta görs det också ett flertal fallstudier och probabilistiska analyser. Ett stort fokus i arbetet har varit att modellen ska vara tillräckligt flexibel för att kunna analysera olika brotyper, samtidigt som mängden indata är begränsad. Följaktligen består modellen av en serie visköst dämpade Bernoulli-Euler balkar som vilar på elastiska upplag. Tåglasten beskrivs med rörliga punktlaster som appliceras direkt på brons överbyggnad utan att interaktion mellan tåg-spår-bro beaktas. Med dessa egenskaper kan modellen användas till att analysera alltifrån fritt upplagda betongbalkbroar till kontinuerliga samverkansbroar. En annan fördel med den föreslagna modellen är att lösningen är exakt eftersom rörelseekvationen har lösts med en Laplacetransform. Resultaten från fallstudierna visar att betongbroar har lägre dynamisk respons om man jämför med stål- och samverkansbroar. Simuleringarna bekräftar också resultat från tidigare studier som visar att broar med korta spann har svårt att uppfylla accelerationskravet. Detta är något som man också har erfarit i Frankrike, där man efter invigningen av höghastighetslinjen mellan Lyon och Paris uppmätte höga accelerationer hos ett flertal korta broar. Vidare visar också analyserna att en kontinuerlig balkbro har upp till 60 % lägre accelerationer jämfört med om samma bro hade utförts som fritt upplagd. / <p>QC 20130529</p>

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